Question

Assertion – The non-fusible impurities present in iron ore are removed by $CaC{O}_3$ .

Reason: $CaC{O}_3$ which decomposes into $CaO$ and $C{O}_2$. The $CaO$ formed reacts with $Si{O}_2$ to remove silica

• A. Both assertion and reason are correct and the reason is the correct explanation for the assertion.
• B. Both assertion and reason are correct but reason is not the correct explanation for the assertion.
• C. Assertion is correct but reason is wrong
• D. Assertion is incorrect but reason is correct
• E. Both assertion and reason are wrong.

Answer 1

The correct option is A

Both assertion and reason are correct and the reason is the correct explanation for the assertion.

Limestone, which is added as part of the feed gets decomposed just above 1000 degree celcius as

$CaC{O}_3$ $\to$ $CaO+C{O}_2$

The lime thus formed, reacts with silica to form fusible slag. Do note that silica is a refractory material and does not melt easily.

$CaO+Si{O}_2$ $\to$ $CaSi{O}_3$

(Fusible slag)

This slag does melt near the zone of fusion and forms a protective liquid layer preventing molten iron from getting oxidized. Now, which would be lighter - the slag or the molten metal?